Oil compositions containing sodium nitrite



United States Patent 3,089,848 on. coMPosrrroNs CONTAINING soorUM Nlli EThis invention relates to lubricating compositions contaming sodiumnitrite as a rust preventive. Particularly, the invention relates tocompositions wherein the efiectiveness of sodium nitrite is enhanced bycertain auxiliary additives and to methods whereby sodium nitrite isdispersed in stable, finely divided form, in lubricating greases.

The use of sodium nitrite as a rust preventive has long been recognizedand it has been proposed to add sodium nitrite to lubricating greases inorder to inhibit rusting of metal surfaces. This rusting can be causedby water or moisture which may become absorbed or entrained in the.grease during use or actually rejected by water repellant greases, thusdirectly contacting metal surfaces.

It has now been found that the use of certain auxiliary additivematerials, specifically, metal naphthenates and fatty acid partialesters of aliphatic polyhydric alcohols (e.-g. sorbitan monooleate),will increase the effectiveness of the sodium nitrite in preventing rustmuch more than would be expected.

In addition, a new method of dispersing sodium nitrite in grease hasalso been found, which overcomes many of the disadvantages of priormethods. One such prior method involved mixing an aqueous solution ofsodium nitrite into the lubricating grease and then heating to evaporatethe water to thereby obtain a homogeneous dispersion of the nitrite inthe grease. However, if the grease contains a soap or salt of a metalother than sodium, particularly divalent metals, then metathesis occursat the high temperature necessary for the evaporation of water. Theresult is that metal of the soap or salt thickener is exchanged bysodium, thereby changing the characteristics of the original grease.This has been found particularly objectionable in the manufacture ofalkaline earth metal greases, e.g. calcium soap grease, since thestructural stability of the grease is down-graded by metathesis with thesodium nitrite. Another disadvantage of this method is that sodiumnitrite crystallizes out of the aqueous solution in the form of ratherlarge particles or crystals. These particles give the grease a grainytexture, as well as increasing its wearing tendency due to the abrasivenature of the sodium nitrite particles. Even when increased wear is nottoo great, the large size crystals give noisy and objectionableanti-friction bearing operation.

Another prior method of dispersing sodium nitrite in grease is disclosedin US. Patent No. 2,738,329. Here, the grease with sodium nitritepresent, is heated to form a hot, fluid composition, i.e. heated to atemperature above the melting point of the grease. Upon cooling of thecomposition, the dropping point of the grease was very materiallyincreased and other changes effected, even by the addition of smallamounts of sodium nitrite. Apparently, some form of complex was formedbetween the grease thickener and the sodium nitrite. Thus, this methodis not applicable Where the aim is only to increase the rust resistanceof the grease, but not to alter any of its other properties.

3,08%,843 Patented May 14, 1963 ice Another prior method involves thesimple addition of powdered sodium nitrite into a finished greasecomposition with stirring. This method, even though the resultingcomposition is homogenized, results in a grainy grease, increases itswearing tendency and frequently causes noisy bearing operation.

In the method of the present invention, sodium nitrite can be added to agrease without affecting any of the other properties of the greaseexcept inhibiting rusting caused by entrained Water. Furthermore, asmooth, homogeneous, non-grainy product is obtained.

In the preferred form of the present method, commercial granular sodiumnitrite is first dissolved in water, preferably boiling water, to form asuper-saturated solution. Then a Water gelling agent is added to gel thesolution which will thereby inhibit growth of any crystals that mayform. Next, this water gel is mixed with an oil solution containing alow molecular weight polymer and the entire mixture is then heated todrive oif the water. As the water evaporates, the sodium nitritecrystals which are forming are coated by the low molecular weightpolymer and their crystal growth is inhibited. The result is an oildispersion of very finely divided sodium nitrite. This oil dispersionmay then be conveniently mixed into the final grease composition, sincethe sodium nitrite concentrate dispersion is readily dispersed in coldor Warm grease compositions with a minimum of mixing.

The sodium nitrite is used in the final grease composition in amounts of0.1 to 3.0 wt. percent, preferably 0.3 to 1.0 wt. percent, based on theweight of the total composition. The auxiliary additives which increasedthe effectiveness of the sodium nitrite are used in amounts of 0.05 to1.0 part by weight, per part by weight of sodium nitrite.

The naphthenates are preferably the zinc or sodium salts of naphthenicacids, preferably having molecular weights of 250 to 350 andneutralization numbers of 225 to 175.

The fatty acid partial ester materials include the C to C fatty acidpartial esters of aliphatic polyhydric alcohols having about 3 to 12,e.g., 3 to 8 carbon atoms, and about 2 to 8, e.g., 3 to 6 hydroxy groupsper molecule. Preferred materials are the monoand diesters of C to Calcohols having about 3 to 6 hydroxyl groups and prepared from C to Cfatty acids. The above type of partial esters includes the partialesters of the monohydrated aliphatic polyhydric alcohols, which are wellknown in the art, for example, see US. Patent 2,434,490, as well aspartial esters of non-dehydrated aliphatic polyhydric alcohols, e.g.pentaerythritol monooleate.

Specific examples of the above types of partial esters will thereforeinclude: glyceryl monooleate, pentaerythritol monooleate, sorbitanmonooleate, the dioleates of sorbitan, mannitan, pentaerythritol andrelated polyhydric alcohols, the corresponding partial stearic andpalmitic acid esters of these alcohols, and partial esters of thesealcohols made from mixtures of these fatty acids.

The rust inhibiting combination may be added to any type of greasecomposition. Included are greases thickened with salts, soaps, soap-saltor mixed salt complexes, polymeric thickeners (e.g. polymers of C to Cmonoolefins of 10,000 to 200,000 molecular weight such as polyethylene),and inorganic thickeners (e.g. clay, carbon black, silica gel, etc).

Generally, the greases will comprise either a synthetic or minerallubricating oil thickened with about 3 to 35 wt. percent, usually 3 to20 wt. percent, of a thickener. In the case of soap-salt and mixed-saltthickeners, the thickener is usually formed by co-neutralization in oil,by metal base, of various mixtures of high molecular weight fatty acidsand/or intermediate molecular weight fatty acids with low molecularweight fatty acids.

The high molecular weight fatty acids useful for forming soap-salt, soapand mixed-salt thickeners include naturally-occurring or synthetic,substituted and unsubstituted, saturated and unsaturated, mixed orunmixed fatty acids having about 14 to 30, e.g. 16 to 22, carbon atomsper molecule. Examples of such acids include stearic, hydroxy stearic,such as 12-hydroxy stearic, di-hydroxy stearic, poly-hydroxy stearic andother saturated hydroxy fatty acids, arachidic, oleic, ricinoleic,hydrogenated fish oil, tallow acids, etc.

Intermediate molecular weight fatty acids include those aliphatic,saturated, unsubstituted, mono-carboxylic acids containing 7 to 12carbon atoms per molecule, e.g., capric, lauric, caprylic, nonanoicacid, etc.

Suitable low molecular weight acids include C to C fatty acids. Aceticacid or its anhydride is preferred.

Metal bases which are frequently used to neutralize the above acids arethe hydroxides, oxides or carbonates of alkali metals (e.g. lithium andsodium) or of alkaline earth metals (e.g. calcium, magnesium, strontiumand barium).

Various other additives may also be added to the lubricating composition(e.g. 0.1 to 10.0 weight percent based on the total weight of thecomposition), for example, oxidation inhibitors such asphenyl-alpha-naphthylamine; tackiness agents such as polyisobutylene;stabilizers such as aluminum hydroxy stearate; and the like.

As previously mentioned, the sodium nitrite and the other additives arepreferably added to the grease in such a way so as to obtain anextremely small particle size. This is best accomplished by dissolvingabout 40 to 60 wt. percent based on total weight of water solution, ofthe combined sodium nitrite and auxiliary enhancing agent in water.Preferably as little water as possible is used to minimize the amount tobe later removed by evaporation. This can be accomplished by using hotwater, e.g. 150- 212 F., preferably boiling Water. Into this hot watersolution, and preferably as quickly as it is formed and before anycrystallization can occur, about 0.1 to 1.0 wt. percent, based on totalweight of water solution, of a water gelling agent is added. The watergelling agent thickens or gells the solution upon cooling tosubstantially immobilize the solution. Thus, any sodium nitrite whichcrystallizes out from the solution is inhibited from growing into largercrystal sizes. Any water gelling or water thickening agent may be used.Preferred are the various ether celluloses such as methyl cellulose,ethyl cellulose or a group of materials sold under the tradename ofJaguar resins. Jaguar is Stein-Halls registered trademark for guar gum,a natural vegetable colloid. Guar gum is a polysaccharide (chemicallyclassified as a galactomannan) consisting of a complex carbohydratepolymer of galactose and mannose. It is non-ionic and therefore will notdegel in the presence of ionic salt solutions. Another particularlyuseful material to prevent the growth of crystals is a carboxy vinylpolymer neutralized with sodium hydroxide. A material of this type whichwas used in several of the examples is Carbopol 934 which has beenneutralized with sodium hydroxide by simple mixing without removing thewater of neutralization.

The above described water dispersion, either hot or cold, is next mixedwith about .25 to 2.0 parts by weight, per part of water solution, of anoil solution of a polymeric material. Preferably polymers havingmolecular Weights of about 5,000 to 100,000 and which are oildispersible can be used. Preferred polymers of this type arepolypropylene and polyethylene, i.e. C to C monoolefin polymers. Suchpolymers are used in amounts of .05 to .15 part by weight, per part byweight of oil.

Next, the combination of the water solution and oil solution is heatedsufficiently to drive off substantially all the Water. The result is astable oil dispersion of the sodium nitrite in a very finely dividedform dispersed in the oil. This oil solution in turn can be added to anygrease composition.

While the above technique represents a preferred method of preparing thecompositions of the invention, it is to be understood that thenaphthenates and/ or partial esters may be used with the sodium nitriteemploying other methods to disperse the nitrite in oil. For example,just simple mixing of finely divided sodium nitrite and the naphthenateand/or partial ester into the grease will give better rust protectionthan a like amount of either material alone. This simple mixing willresult in a grainy grease giving noisy bearing operation as previouslymentioned. However, while less preferred, this method may be used whengraininess or noisy bearing operation are not important considerations.

The invention will be further understood by the following examples:

EXAMPLE I (All parts by weight) Inhibitor concentrate 1.-50 parts ofsodium nitrite was dissolved in 50 parts of hot water while maintaininga temperature of 210 F. 0.5 part of Carbopol 934 (carboxy vinyl polymer)neutralized with sodium hydroxide in 0.2 part of water was next added,while boiling the sodium nitrite aqueous solution. After all theneutralized Carbopol 934 had been added and while still boiling thesolution, there was next added 50 parts of an oil dispersion consistingof 10 wt. percent of atactic polypropylene having an average molecularweight of about 50,000, 1 wt. percent Span (sorbitan monooleate) and 89wt. percent of a mineral lubricating oil having a viscosity of 55 SUS at210 F. Boiling of the entire mixture was continued until all the waterhad been removed. The resulting dispersion had the followingcomposition:

Percent Sodium nitrite 49.5 Neutralized Carbopol 934 0.5 Atacticpolypropylene 5.0 Span 80 (sorbitan monooleate) 0.5 Mineral oil 44.5

Inhibitor concentrate 2.-The above preparation was repeated to form asecond inhibitor concentrate but which contained no Span 80 whatsoeverand instead contained 50.0 wt. percent sodium nitrite.

Inhibitor concentrate 3.A third inhibitor concentrate was prepared bydispersing 50 wt. percent of sodium nitrite in 50 wt. percent of amineral oil having a viscosity of 55 SUS at 210 F. The sodium nitriteused was one of the most finely divided sodium nitrites available havingan average particle size of about 35 microns.

Portions of each of the above inhibitor concentrates 1 to 3 were addedby simple mixing at room temperature, in the amounts of 1, 2, 3 and 4wt. percent, respectively, based on the weight of the total composition,to a calcium salt grease.

The calcium salt grease was prepared by neutralizing with lime, amixture of acetic acid and Wecoline AAC acids (a mixture of C C and Cfatty acids having an average molecular weight of about The neutralizedmixture of acids was heated to a temperature of about 440 F. anddehydrated. About 6 moles of acetic acid were used per mole of WecolineAAC acid. The total amount of thicknener constituted about 22 wt.percent of the grease, while its oil base was a mineral lubricating oilof 55 SUS viscosity at 210 F. After cooking at a temperature of 440 F.the grease was cooled to about mill.

These grease compositions containing the various inhibitor concentrateswere tested by the CRC L-41 procedure which is an ASTM Tentative Methodof Test for: Rust Preventive Properties of Lubricating Greases. Brieflystated this procedure involves taking a clean small Timken rollerbearing, coating and packing the bearing with grease, rotating thehearing at 1750 rpm. under a load of 6 lbs. for one minute, then dippingthe bearing in freshly boiled distilled water, followed by storing thebearing over water in a sealed jar for 14 days so as to provide a humidatmosphere. At the end of 14 days' the bearing is cleaned and examinedfor rust. The bearing is then rated on a scale, wherein R-l representsno rust whatsoever, R-Z represents no more than 2 faint rust spots, andR-3 represents more than 2 faint rust spots. R-3 is considered acomplete failure, while R-1 and R-Z are considered as passing. Bearingshaving large rust spots were considered as failing badly.

The compositions prepared above, including the base grease without anyrust preventive whatsoever, were tested by the above procedure. Theresults obtained are summarized in the following table:

Table 1 RESULTS or ORG L-41 RUST TEST The grease without inhibitorfailed badly.

1. Contains oil, sodium nitrite, neutralized Carbopol 934, polypropyleneIlbibfiiis oil, sodium nitrite, neutralized Carbopol 934, polypropylene,(no Span 80).

3. Simple oil concentrate of sodium nitrite.

As seen by the above table, the compositions containing both the sodiumnitrite and Span 80 (inhibitor concentrate 1) were very successful inthe corrosion test even when used in an amount as low as 1 weightpercent of inhibitor concentrate. On the other hand, by leaving out theextremely small amount of Span 80 involved, it required 4% of theinhibitor concentrate in order to effectively inhibit the rusting asshown by the results obtained when using inhibitor concentrates 2 and 3.

A second grease was prepared and all of the above tests repeated. Thesecond grease was formed by nontralizing 13 parts of hydrated lime with15.1 parts of acetic anhydride and 9.4 parts of Emery 32865 acid (atreated vegetable fatty acid consisting mainly of iso-oleic acid) in61.5 parts of mineral lubricating oil having a viscosity of 55 SUS at210 F., to which was added one part of phenyl-alpha-naphthylamine, (allparts are by weight). The neutralized mixture was dehydrated at atemperature of about 300 F. Exactly the same results were obtained withthe second grease as were reported in Table 1.

EXAMPLE -II A base grease was prepared (wherein all parts are byweight), by dispersing 9.4 parts of tallow fatty acids and 13 parts ofhydrated lime in 61.5 parts of mineral lubricating oil having aviscosity of 55 SUS at 210 F. These materials were mixed together atroom temperature, and while stirring, 15.1 parts of acetic anhydride wasslowly added, the temperature rising to a maximum of 180 F. After allthe anhydride was added, external heating was initiated and thetemperature of the composition increased to 320 F. in order to dehydratethe grease. At this point, 1 part of phenyl-alpha-naphthylamine wasadded as an oxidation inhibitor and the grease was allowed to cool to 90F. The grease was then passed through a Morehouse mill having an 0.003"clearance. The resulting product had a dropping point above 500 F. andan ASTM unworked penetration at 77 F. of 323 mm./ 10, which upon working10,000 strokes decreased only to 319 mm./ 10. The grease was alsoinsoluble in both hot and cold water.

To the above base grease, was added sodium nitrite having an averageparticle size of 35 microns and zinc naphthenate in varying amounts. Thezinc naphthenate was the zinc salt of a 250 molecular weight naphthenicacid obtained from a petroleum diesel oil fraction. These two materialswere incorporated by mixing directly into the grease and then twicehomogenizing in a Morehouse mill in order to thoroughly disperse theadditive in the grease. Other samples were made up using the sodiumnitrite and naphthenate alone. These various samples were then subjectedto CRC L-41 test procedure described above. The results obtained aresummarized in the following table:

Table II RUST TESTSCRC L-4l PROCEDURE Amount of Additive 1 Results ofRust Test None Fail (R-3), Badly rusted. 1% Zinc Naph. Fail (R-3).

2% Zinc Naph 2% NaNOz (35p) 1.0% NaNOa (3511).- 0.5% NaNOz (35 4)-.0.25% Zine Naph...

Badly rusted. Pass (R 1), Unaffected, no rust spots or stains. Fail(It-3), Badly rusted. }Pass (R-l), Excellent protection.

1 Wt. percent based on the weight of the total composition.

EXAMPLE III A colloidal sodium nitrite concentrate base was prepared inthe same general manner described above in Example I. The finishedconcentrate had the following composition:

Composition of concentrate: Percent wt. Water 2.00 Sodium nitrite 49.0Carbopol 934 (neutralized) 0.13 Span 80 0.05 Atactic polypropylene 5.00

Mineral oil of 55 SUS. viscosity at 210 F 43.82

This concentrate was prepared as follows:

The sodium nitrite was added to an equal amount by weight of water andthe mixture heated to boiling to completely dissolve all the nitrite. Tothis hot saturated aqueous solution was added a dispersion of Carbopol934 dispersed in an amount of water equal to /2 the amount of water usedin dissolving the sodium nitrite. After all the dispersion of Carbopol934 had been added to the boiling water solution of sodium nitrite, andwhile still boiling, an oil solution of polypropylene was added. Thispolypropylene had a molecular weight of about 50,000. Evaporation ofwater was continued until about only 2 wt. percent of the totalcomposition was water, after which the material was cooled andhomogenized in a Morehouse mill at 0.003" clearance. This small amountof water present is desirable since it allows easier handling, resultsin smaller particle sizes and later gives 7 greater dispersion of theinhibitor concentrate in the oil. However, if desired, the inhibitorconcentrate could be evaporated to complete dryness.

Four grease compositions were prepared in the same substantially all ofsaid Water to thereby form a dispersion in said oil of polymer-coatedsodium nitrite having an average particle size less than about 15microns.

3. A method according to claim 2, wherein said olefin general manner asin Example II, but using the inhibitor .5 polymer is polypropylene.concentrate described immediately above. The composi- 4. A method ofdispersing sodium nitrite in an oil tions of these greases aresummarized in the following which comprises forming a solution of about40 to 60 table along with their properties: wt. percent, based on theweight of said solution, of so- Table III Formulation (Percent Weight)Grease A Grease B Grease O Grease D Acetic Acid 10.0.. 12.9 12.9. AceticAnhydride.- 14.0.- Wccoline AAO Acid 5.0.. 3 9-. 3 9 Tallow fatty acid8.7.. l2rhydroxy stearic acid... 0 2.0 2.0. Hydrated lime 8.3.. 12.08.6.. 8.6. PhenyM-naphthylamine. 1.0... 1.0.. 0.3.. 0.3. Mineral oil71.7.. 60.3... 71.0 67.9. NaNOz Concentrate 4.0.. 4.0-. 0.0... 4.0.Appearance F' ut Excellent Fxcellent Excellent, Dropping Point, F 500500+ 500+. Penetrations, 77 F., mm./10:

Unworked 320 310 271 269.

Worked 60 strokes 330-... 315 291 208.

Worked 10,000 strokes Semi-Flui 317 304 377.

Rust Tests: ORG L-41 Method, Rating...- R-l (No rusting).. R-l (N0rusting) R-3 (Fails) R-l (N o rusting). Microscopic examinationdetermination of p size of the sodium nitrite in microns About 10 About10 About 10.

As seen by the above table, grease C which contained diurn nitrite inboiling water; adding about 0.1 to 1.0 no sodium nitrite failed in therust test, While greases A, wt. percent, based on the weight of saidsolution, of a B and D gave no rusting and had good all around propwatergelling agent to the boiling water solution of soerties. Furthermore,the preferred method of the invendium nitrite to thereby inhibit crystalgrowth of said sotion resulted in sodium nitrite particles of about 10dium nitrite; adding to the resulting water solution, about micron size,while other common methods of forming 0.25 to 2.0 parts by weight, perpart by Weight of Water sodium nitrite crystals result in largerparticle size. Thus, solution, of an oil solution comprising 5 to 15 wt.percent the method can give particle sizes of 15 microns or less, of a Cto C olefin polymer of 5,000 to 100,000 molecuwhile commercial sodiumnitrite is of about 35 micron lar weight, heating the resulting mixtureto evaporate size. Simple evaporation of aqueous solutions of sodiumsubstantially all of said water to thereby form a dispernitrite in oilwill also give a micron size of 35 or higher. sion in said oil of sodiumnitrite having an average parti- As mentioned above, such largerparticles (i.e. about 35 cle size less than about 15 microns. microns)give a gritty texture to the grease and causes 5. A method according toclaim 4, wherein there is noisy bearing operation which is avoided bythe method added to said boiling water, about 0.05 to 1.0 part by of theinvention. Weight, per part by weight of sodium nitrite, of a ma- Insummary, the present invention primarily relates terial selected fromthe group consisting of zinc and soto additive combinations of sodiumnitrite with zinc or diurn salts of naphthenic acid of 250 to 350molecular sodium naphthenate and/ or certain partial esters. The weightand C to C fatty acid partial esters of C to invention further relatesto a new method of forming C aliphatic polyhydric alcohols having 3 to 6hydroxy finely divided sodium nitrite in oil. The additive combigroups.nations are best used in the form of oil concentrates com- 6. A methodaccording to claim 5, wherein said maprising about 20 to 60 wt. percentadditive and 80 to 40 terial is sorbitan monooleate. wt. percent oil,preferably mineral oil, although of course 7. A method according toclaim 5, wherein said oil any less amount of additive in oil can beused. is a mineral lubricating oil.

What is claimed is: 8. A rust inhibitor composition comprising sodiumni- 1. A method of forming a stable dispersion of finely trite dispersedin oil, which is prepared by forming a soludivided sodium nitrite inoil, said dispersion being useful tion of sodium nitrite in water,adding to said solution a as a rust preventive additive, which comprisesforming a water gelling agent to gel said solution to thereby inhibitsolution of sodium nitrite in water, adding to said solucrystal growthof said sodium nitrite, adding to said solution a water gelling agent togel said solution to thereby tion an oil solution of an oil-solublehydrocarbon polymer inhibit crystal growth of said sodium nitrite,adding to having a molecular weight of from 5,000 to 100,000 to saidsolution an oil solution of an oil-soluble hydrocarcoat said sodiumnitrite, heating the resulting mixture bon polymer having a molecularweight of from about to evaporate substantially all of said water tothereby 5,000 to 100,000 to coat said sodium nitrite, heating the form adispersion in said oil of polymer-coated sodium resulting mixture toevaporate substantially all of said nitrite having an average particlesize less than about water to thereby form a dispersion in said oil ofpoly- 15 microns. mar-coated sodium nitrite having an average particle 59. A rust inhibitor composition prepared by forming size less than about15 microns. a solution of 40 to 60 wt. percent, based on the Weight of2. A method of forming a stable dispersion of finely said solution ofsodium nitrite in boiling water; adding divided sodium nitrite in oil,said dispersion being useful about 0.1 to 1.0 wt. percent, based on theweight of said as a rust preventive additive, which comprises forming asolution, of a water gelling agent to the boiling water solution ofsodium nitrite in water, adding to said solu 7 solution of sodiumnitrite; adding to the resulting water tion a water gelling agent to gelsaid solution to thereby solution, about 0.25 to 2.0 parts by weight perpart by inhibit crystal growth of said sodium nitrite, adding to weightof water solution, of an oil solution comprising said solution an oilsolution of a C to C olefin polymer 5 to 15 wt. percent of a C to Colefin polymer of 5,000 of 5,000 to 100,000 molecular weight to coatsaid soto 100,000 molecular weight; adding about 0.05 to 1.0 diumnitrite, heating the resulting mixture to evaporate 7 part by Weight,per part by Weight of sodium nitrite, 0f

a material selected from the group consisting of zinc and sodium saltsof naphthenic acid of 200 to 350 molecular weight and C to C fatty acidpartial esters of C to C aliphatic polyhydric alcohols having 3 to 6carboxy groups and heating the resulting mixture to evaporatesubstantially all of said water to thereby form a dispersion in said oilof sodium nitrite having an average particle size less than about 15microns.

References Cited in the file of this patent UNITED STATES PATENTSHollabaugh et al.:

10 Kroenig et a1. Jan. 24, 1956 Parry et al. Mar. 13, 1956 Cooke et a1Aug. 14, 1956 Blake Dec. 19, 1961 FOREIGN PATENTS Great Britain July 10,1957 Canada Nov. 11, 1958 OTHER REFERENCES Carboxymethylcellulose Usesand Applications, in Industrial and Engineering Chemistry, vol. 37, No.10, October 1945, p. 946 relied

1. A METHOD OF FORMING A STABLE DISPERSION OF FINELY DIVIDED SODIUMNITRITE IN OIL, SAID DISPERSION BEING USEFUL AS A RUST PREVENTIVEADDITIVE, WHICH COMPRISES FORMING A SOLUTION OF SODIUM NITRITE IN WATER,ADDING TO SAID SOLUTION A WATER GELLING AGENT TO GEL SAID SOLUTION TOTHEREBY INHIBIT CRYSTAL GROWTH OF SAID SODIUM NITRITE, ADDING TO SAIDSOLUTION AN OIL SOLUTION OF AN OIL-SOLUBLE HYDROCARBON POLYMER HAVING AMOLECULAR WEIGHT OF FROM ABOUT 5,000 TO 100,000 TO COAT SAID SODIUMNITRITE, HEATING THE RESULTING MIXTURE TO EVAPORATE SUBSTANTIALLY ALL OFSAID WATER TO THEREBY FORM A DISPERSION IN SAID OIL OF POLYMER-COATEDSODIUM NITRITE HAVING AN AVERAGE PARTICLE SIZE LESS THAN ABOUT 15MICRONS.